Conditions for Setting the DTC
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The ECM detects a start-up temperature difference between the ECT sensor and the IAT sensor 2 of more than 15°C (59°F). If the ECT temperature decreases more than 5°C (41.5°F), with an engine RPM greater than 650 within the first 60 seconds of engine run time, a block heater is detected and the test is aborted. If the ECT temperature does not decrease, a block heater was not detected and DTC P0116 sets.